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Title: Mechanism of field-reentrant superconductivity in UTe2 above 400 kG
Plain: In UTe2, superconductivity reappears in magnetic fields of about 400 to 650 kG when the field is tilted at a particular angle, fields far above those that destroy ordinary superconductors.
Precise: In UTe2 with the field tilted from the b axis toward c by roughly 20 to 40 degrees, superconductivity reappears above the metamagnetic transition $H_m \sim 350\,\mathrm{kG}$ and survives to $\sim 650\,\mathrm{kG}$ (Ran et al., Nature Physics 2019). Determine the pairing mechanism and order parameter of this field-polarized phase: triplet pairing mediated by field-enhanced ferromagnetic fluctuations, compensation of the exchange field by the applied field (Jaccarino-Peter mechanism), or pairing on a Fermi surface reconstructed at $H_m$. An answer predicts the angular window and the upper critical field from a model with independently measured parameters.
Settled by: Fermi-surface and magnetization measurements across $H_m$ combined with a calculation that reproduces the angular window and upper field of the reentrant phase.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: contested
Status note: Helm et al. (Nature Communications 2024) proposed field-induced compensation of magnetic exchange; no mechanism is agreed.
Posed since: 2019